The present invention relates to a liquid dynamic pressure bearing and to a spindle motor, a hard-disk driving unit, and,a scanner motor using the bearing and constructed so that the bearing supports a load by means of liquid dynamic pressure of oil drawn by rotation in a groove formed at either or both of a rotating face and a static face.
A bearing construction in which a rotor shaft is supported by a liquid dynamic pressure bearing is well known and is used in various kinds of motors and the like. It has previously been attempted to realize stable rotation resistance to external shock by a construction supporting both ends of the liquid dynamic pressure bearing as disclosed in Japanese Laid-Opened Utility Model No. 57-12828, for example.
However, both ends of a liquid region for lubrication formed between the rotating face and the static face are left open if it is attempted to provide support with both ends of the bearing in the liquid dynamic pressure bearing. Therefore, liquid for lubrication has a problem in that sealing is not adequate and leakage of liquid occurs easily because only surface tension and viscosity of liquid must support the liquid in the predetermined region.
Moreover, the construction opened at both ends has problems in that the area where liquid for lubrication contacts air increases sharply, the speed of evaporation of the liquid for lubrication becomes high, and the condition of lubrication between the rotating face and the static face becomes insufficient.
An object of the present invention is to provide a liquid dynamic pressure bearing and a spindle motor, a hard disk driving unit, and a scanner motor supporting both ends of a rotor shaft stably by the liquid dynamic pressure bearing without the above-mentioned inconvenience.
To achieve the above-object, a liquid dynamic pressure bearing in a first aspect of the present invention has the characteristics that it is a liquid dynamic pressure bearing for supporting a rotor shaft; it has a pair of liquid dynamic pressure bearings for supporting both ends of the rotor shaft; the pair of liquid dynamic pressure bearings keep the predetermined liquid for lubrication in a clearance having only one opening portion; and a journal bearing is formed in a common axis at least at one side of one of the liquid dynamic pressure bearings.
The pair of liquid dynamic pressure bearings may be conical in shape at a bearing face thereof in a second aspect.
The pair of liquid dynamic pressure bearings may be disk shape at a bearing face thereof in a third aspect.
A capillary oil-sealing portion may be formed at the opening portion in a fourth aspect.
A liquid receiver for receiving liquid between an edge end of the journal bearing and the facing rotor shaft is provided in a fifth aspect.
A spindle motor supporting the rotor by liquid dynamic pressure bearing of the present invention is characterized by the following characteristics: the spindle motor has a pair of liquid dynamic pressure bearing portions with which the liquid dynamic pressure bearings support both ends of the rotor shaft; the pair of liquid dynamic pressure bearing portions keep the predetermined liquid for lubrication with clearance having only one opening portion; and a journal bearing is formed in common axis at least at one side at the one liquid dynamic pressure bearing portion in a sixth aspect.
The pair of liquid dynamic pressure bearing portions may be conical in shape at the bearing face thereof in a seventh aspect.
The pair of liquid dynamic pressure bearing portions may be disk shaped at the bearing face thereof in an eighth aspect.
A capillary oil-sealing portion may be formed at the opening portion in a ninth aspect.
A liquid receiver for receiving the liquid between an edge end of the journal bearing and the facing rotor shaft is provided in a tenth aspect.
A rotating driving source and a load of the spindle motor may be arranged between the pair of liquid dynamic pressure bearings in an eleventh aspect.
The load may be surrounded with a cover in a twelfth aspect.
A hard disk driving unit attaching magnetic disk media at a rotor: shaft supported by liquid dynamic pressure bearings according to the present invention is characterized by the following: the driving unit has a pair of liquid dynamic pressure bearing portions which the liquid dynamic pressure bearings support each both ends of the rotor shaft; the pair of liquid dynamic pressure bearing portions keep the predetermined liquid for lubrication with clearance having only one opening portion; and a journal bearing is formed in common axis at least at one side at the one liquid dynamic pressure bearing portion in a thirteenth aspect.
The pair of liquid dynamic pressure bearing portions may be conical in shape at the bearing face thereof in a fourteenth aspect.
The pair of liquid dynamic pressure bearing portions may be disk shaped at the bearing face thereof in a fifteenth aspect.
A capillary oil-sealing portion may be formed at the opening portion in a sixteenth aspect.
A liquid receiver for receiving liquid between edge end of the journal bearing and the facing rotor shaft is provided in a seventeenth aspect.
A driving source for rotating the rotor shaft and magnetic disk media may be arranged between the pair of liquid dynamic pressure bearings in an eighteenth aspect.
The magnetic disk media may be surrounded with a cover in a nineteenth aspect.
Between the liquid dynamic pressure bearing portion and the magnetic disk media, a projected trap for shorten air clearance of border of them may be formed in a twentieth aspect.
A scanner motor attaching a rotating polygon mirror at a rotor shaft supported by liquid dynamic pressure bearings of the present invention is characterized by the following: the scanner motor has a pair of liquid dynamic pressure bearing portions which the liquid dynamic pressure bearings support each of both ends of the rotor shaft; the pair of liquid dynamic pressure bearing portions keep the predetermined liquid for lubrication with clearance having only one opening portion; and a journal bearing is formed in common at least one side at the one liquid dynamic pressure bearing portion in a twenty-first aspect.
The pair of liquid dynamic pressure bearing portions may be conical in shape at the bearing face thereof in a twenty-second aspect.
The pair of liquid dynamic pressure bearing portions may be disk shaped at the bearing face thereof in a twenty-third aspect.
A capillary oil-sealing portion may be formed at the opening portion in a twenty-fourth aspect.
A liquid receiver for receiving the liquid between edge end of the journal bearing and the facing rotor shaft is provided in a twenty-fifth aspect.
A driving source for rotating the rotor shaft arid a rotating polygon mirror may be arranged between the pair of liquid dynamic pressure bearings in a twenty-sixth aspect.
The rotating polygon mirror may be surrounded with a cover in a twenty-seventh aspect.
Between the liquid dynamic pressure bearing portion and the magnetic disk media, a projected trap for shortening air clearance an a border therebetween may be formed in a twenty-eighth aspect.
The liquid dynamic pressure bearings of the present invention keep lubrication oil for generating dynamic pressure with clearance and having only one opening portion. That can keep lubrication oil inside of the bearing so that leakage of lubrication oil is suppressed.
In the spindle motor of the present invention, both ends of the rotor shaft are supported by the liquid dynamic pressure bearings, and between the pair of liquid dynamic pressure bearings, the rotating driving source and the load are formed near the center of gravity of the bearing at the rotor shaft. Therefore, the spindle motor is resistant to external shock.
In the hard disk driving unit of the present invention, the magnetic disk media formed at the rotor shaft of the spindle motor as a load so as to prevent precession of the rotor. Therefore, rotation of the magnetic disk media can be stabilized.
In the scanner motor of the present invention, the rotating polygon mirror is formed at the rotor shaft of the spindle motor as a load so as to prevent precession of the rotor. Therefore, scanning of the rotating polygon mirror can be performed accurately without fluctuation.